Base station, radio terminal, and methods therein

ABSTRACT

A radio terminal ( 1 ) receives from a base station ( 2 ) a first value ( 601 ) of a first radio resource configuration information element. The first value ( 601 ) is associated with normal coverage or with a first coverage enhancement level. The radio terminal ( 1 ) derives a second value ( 604 ) of the first radio resource configuration information element by converting ( 603 ) the first value ( 601 ) using a value of a conversion factor ( 602 ). The second value ( 604 ) is associated with a second coverage enhancement level. It is thus, for example, possible to contribute to reduction of data size necessary for the base station to notify the radio terminal of a plurality of radio resource configurations for a plurality of coverage enhancement levels.

CROSS REFERENCE TO RELATED APPLICATIONS

This is a Continuation application of application Ser. No. 15/757,432,filed on Mar. 5, 2018, which is a National Stage of InternationalApplication No. PCT/JP2016/004157 filed Sep. 13, 2016, claiming prioritybased on Japanese Patent Application No. 2015-217963 filed Nov. 5, 2015.The entire disclosures of all the prior applications are considered partof the disclosure of this application and are hereby incorporated byreference in their entirety.

TECHNICAL FIELD

The present disclosure relates to a radio communication systemconfigured to perform communication control for coverage enhancement.

BACKGROUND ART

In the 3rd Generation Partnership Project (3GPP), standardization oftechniques for improving deterioration of communication quality due torecent sharp increase in mobile traffic and for achieving fastercommunication has been performed. Further, standardization of techniquesfor avoiding an increase in a control signaling load due to connectionsof an enormous number of Machine to Machine (M2M) terminals to a LongTerm Evolution (LTE) or LTE-Advanced network has been performed. The M2Mterminals are, for example, terminals that perform communication withouthuman intervention. The M2M terminals are placed in various types ofequipment including machines (e.g., vending machines, gas meters,electric meters, vehicles, railway vehicles, and ships) and sensors(e.g., environmental, agricultural, and traffic sensors). In the LTE andLTE-Advanced, communications performed by the M2M terminals is referredto as Machine Type Communication (MTC) and a terminal performing the MTCis referred to as an MTC terminal (i.e., MTC User Equipment (MTC UE)).

While M2M service providers need to distribute an enormous number of M2Mterminals, there is a limit to the cost allowable for each M2M terminal.Therefore, it is required that M2M terminals be implemented at a lowcost, and M2M terminals be able to perform communication with low powerconsumption, for example. Further, in one use case, MTC UEs performcommunication while they are fixedly or statically installed inbuildings. In this case, the radio quality of the MTC UEs may be alwayslow and accordingly coverage enhancement technique is especially neededfor the MTC UEs compared to normal UEs having mobility (e.g., mobiletelephones, smartphones, tablet computers, and notebook personalcomputers (notebook PCs)). Further, functional restrictions contributingto reduction of the cost include, for example, a low maximumtransmission power, a small number of reception antennas (e.g., only onereception antenna), no support of high-order modulation schemes (e.g.,64 quadrature amplitude modulation (64QAM)), and a narrow operatingbandwidth (e.g., 1.4 MHz), which lower the maximum transmission rate ofthe MTC UEs.

Therefore, in the 3GPP, standardization of techniques for improving orenhancing communication characteristics of MTC UEs (i.e., coverage),which are expected to be lower than those of normal UEs, has beenperformed (Non-Patent Literature 1). The following description providessome examples of the techniques for enhancing coverage of MTC UEsdiscussed in the 3GPP. It can be said that the coverage enhancementtechniques (or coverage enhancement processing) for MTC UEs describedbelow are processing for improving or enhancing communicationcharacteristics or communication quality of MTC UEs. The state of a UEto which these special coverage enhancement techniques have been appliedis referred to as a Coverage Enhancement (CE) Mode, a Coverage Extension(CE) Mode, an Enhanced Coverage Mode (ECM), or an Extended Coverage Mode(ECM).

The coverage enhancement techniques can improve, for example, areception characteristic of a Physical Broadcast Channel (PBCH), atransmission characteristic of a Physical Random Access Channel (PRACH)preamble (i.e., detection characteristic in a radio base station (anevolved NodeB (eNB))), a reception characteristic of a Physical DownlinkControl Channel (PDCCH), a reception characteristic of a PhysicalDownlink Shared Channel (PDSCH), a transmission characteristic of aPhysical Uplink Control Channel (PUCCH), and a transmissioncharacteristic of a Physical Uplink Shared Channel (PUSCH). The PBCH isa downlink broadcast channel used by an eNB to transmit common broadcastinformation in a cell. The PRACH is an uplink physical channel used by aUE for an initial access (i.e., a random access) to an eNB. The PDCCH isa downlink physical channel used for, for example, schedulinginformation of downlink data (DL assignment) and transmission of radioresource allocation information of uplink data (UL grant) by an eNB. ThePDSCH is a downlink physical channel used for reception of systeminformation and data by a UE. The PUSCH is an uplink physical channelused for data transmission by a UE.

One processing that is being discussed to improve the receptioncharacteristic of the PBCH is to repeatedly transmit broadcastinformation about the PBCH a number of extra times as compared to thenormal operation by a certain number of times (see Non-Patent Literature2). One processing that is being discussed to improve the transmissioncharacteristic of the PRACH is to repeatedly transmit the PRACH (i.e.,preamble) a certain number of times (see Non-Patent Literature 3).Further, one processing that is being discussed to improve the receptioncharacteristic of the PDSCH and the transmission characteristic of thePUCCH and the PUSCH is to repeatedly transmit the PDSCH, the PUCCH, andthe PUSCH over multiple subframes (see Non-Patent Literature 4).Further, one processing that is being discussed to improve the receptioncharacteristic of an M-PDCCH, which is a PDCCH to transmit L1/L2 controlinformation for MTC UEs, is to repeatedly transmit the M-PDCCH overmultiple subframes. According to the above processing, communicationcharacteristics of MTC UEs that are expected to be lower than those ofnormal UEs will be improved. When downlink data is scheduled byrepetitive transmission of the M-PDCCH, it has been discussed totransmit this data at a subframe after the subframe at which the lastrepetitive transmission of the M-PDCCH is performed. It has further beendiscussed to include the number of repetitions of the M-PDCCH (thenumber of repetitions to be actually performed) in downlink (DL) controlinformation contained in this M-PDCCH.

The number of repetitions of transmission and the number of repetitionsof reception that are required for improvement of the communicationcharacteristics depend on the place where am MTC UE is installed and thepathloss between the MTC UE and the eNB. Therefore, the coverageenhancement technique provides a plurality of coverage enhancementlevels (CE levels). The coverage enhancement levels (CE levels) may alsobe referred to as enhanced coverage levels, coverage extension levels,extended coverage levels, or repetition levels (e.g., PRACH repetitionlevels). Further, a one-to-one relation or a certain relative relationmay be configured in advance between the CE level and the Repetitionlevel.

For example, the coverage enhancement technique provides three CE levelsin addition to normal coverage (zero coverage extension). The CE levelsare associated respectively with different numbers of repetitions oftransmission and with different numbers of repetitions of reception. Thenumber of repetitions of transmission and the number of repetitions ofreception used in a high CE level are larger than those used in a low CElevel. Each MTC UE is allocated to a higher CE level, as the pathlossbetween the MTC UE and the eNB increases. In some implementations, anMTC UE measures a Reference Signal Received Power (RSRP) from the eNB ormeasures an estimated pathloss between the MTC UE and the eNB,determines (or estimates) a required CE level based on the measured RSRPor pathloss, and then transmits a random access preamble (RACH preamble)in accordance with the maximum number of repetitions of transmissionassociated with the determined CE level (see Patent Literature 1).

CITATION LIST Patent Literature

-   [Patent Literature 1] International Patent Publication No. WO    2015/021315

Non-Patent Literature

-   [Non-Patent Literature 1] 3GPP TR 36.888 V12.0.0 (2013-06), “3rd    Generation Partnership Project; Technical Specification Group Radio    Access Network; Study on provision of low-cost Machine-Type    Communications (MTC) User Equipments (UEs) based on LTE (Release    12)”, June 2013-   [Non-Patent Literature 2] 3GPP R1-135943, Vodafone, “Way Forward on    P-BCH for MTC enhanced coverage”, 3GPP TSG RAN WG1#75, San    Francisco, USA, 11-15 Nov. 2013-   [Non-Patent Literature 3] 3GPP R1-135944, Vodafone, “Way Forward on    PRACH for MTC enhanced coverage”, 3GPP TSG RAN WG1#75, San    Francisco, USA, 11-15 Nov. 2013-   [Non-Patent Literature 4] 3GPP R1-136001, Vodafone et al. “Way    forward on PDCCH, PDSCH, PUCCH and PUSCH for MTC enhanced coverage”,    3GPP TSG RAN WG1#75, San Francisco, USA, 11-15 Nov. 2013

SUMMARY OF INVENTION Technical Problem

An eNB needs to provide an MTC UE that supports the coverage enhancementtechnique with a plurality of radio resource configurations for aplurality of CE levels. For example, the eNB uses system information forMTC UEs (i.e., System Information Block x-bis (SIB x-bis)), such asSIB1-bis or SIB2-bis, to transmit in a cell a radio resourceconfiguration for an initial access (i.e., random access) performed byan MTC UE in an idle state. If the system information needs toexplicitly include a plurality of radio resource configurations for aplurality of CE levels, the data size of the system informationincreases.

One of the objects to be attained by embodiments disclosed herein is toprovide an apparatus, a method, and a program that contribute toreduction of data size (i.e., signaling overhead) necessary for a basestation to notify a radio terminal of a plurality of radio resourceconfigurations for a plurality of coverage enhancement levels. It shouldbe noted that this object is merely one of the objects to be attained bythe embodiments disclosed herein. Other objects or problems and novelfeatures will be made apparent from the descriptions in thespecification and the accompanying drawings.

Solution to Problem

In a first aspect, a base station includes a memory and at least oneprocessor coupled to the memory. The at least one processor isconfigured to transmit to a radio terminal a first value of a firstradio resource configuration information element and information about aconversion factor. The first value is associated with normal coverage orwith a first coverage enhancement level. The value of the conversionfactor obtained from the information about the conversion factor is usedby the radio terminal to derive a second value of the first radioresource configuration information element. The second value isassociated with a second coverage enhancement level.

In a second aspect, a method in a base station includes transmitting toa radio terminal a first value of a first radio resource configurationinformation element and information about a conversion factor. The firstvalue is associated with normal coverage or with a first coverageenhancement level. The value of the conversion factor obtained from theinformation about the conversion factor is used by the radio terminal toderive a second value of the first radio resource configurationinformation element. The second value is associated with a secondcoverage enhancement level.

In a third aspect, a radio terminal includes a memory and at least oneprocessor coupled to the memory. The at least one processor isconfigured to execute at least one module. The at least one moduleincludes a reception module and a calculation module. The receptionmodule is configured to receive from a base station a first value of afirst radio resource configuration information element. The first valueis associated with normal coverage or with a first coverage enhancementlevel. The calculation module is configured to derive a second value ofthe first radio resource configuration information element by convertingthe first value using a value of a conversion factor. The second valueis associated with a second coverage enhancement level.

In a fourth aspect, a method in a radio terminal includes: (a) receivingfrom a base station a first value of a first radio resourceconfiguration information element, the first value being associated withnormal coverage or with a first coverage enhancement level; and (b)deriving a second value of the first radio resource configurationinformation element by converting the first value using a value of aconversion factor, the second value being associated with a secondcoverage enhancement level.

In a fifth aspect, a program includes instructions (software codes)that, when loaded into a computer, cause the computer to perform themethod according to the above-described second or fourth aspect.

Advantageous Effects of Invention

According to the above-described aspects, it is possible to provide anapparatus, a method, and a program that contribute to reduction of datasize (i.e., signalling overhead) necessary for a base station to notifya radio terminal of a plurality of radio resource configurations for aplurality of coverage enhancement levels.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a diagram showing a configuration example of a radiocommunication network according to several embodiments;

FIG. 2 is a sequence diagram showing an example of an operation oftransmitting system information according to a first embodiment;

FIG. 3 is a diagram showing an example of repetitive transmission of aRACH preamble;

FIG. 4 is a diagram showing an example of values of a radio resourceconfiguration information element for a plurality of CE levels;

FIG. 5 is a flowchart showing an example of operations of a radioterminal according to the first embodiment;

FIG. 6 is a diagram showing a first example of calculations for derivinga radio resource configuration information element by the radio terminalaccording to the first embodiment;

FIG. 7 is a diagram showing a second example of the calculations forderiving a radio resource configuration information element by the radioterminal according to the first embodiment;

FIG. 8 is a diagram showing a third example of the calculations forderiving a radio resource configuration information element by the radioterminal according to the first embodiment;

FIG. 9 is a diagram showing a fourth example of the calculations forderiving a radio resource configuration information element by the radioterminal according to the first embodiment;

FIG. 10 is a diagram showing an example of a random access procedureaccording to the first embodiment;

FIG. 11 is a block diagram showing a configuration example of a radioterminal according to the several embodiments; and

FIG. 12 is a block diagram showing a configuration example of a basestation according to the several embodiments.

DESCRIPTION OF EMBODIMENTS

Specific embodiments are described hereinafter in detail with referenceto the drawings. The same or corresponding elements are denoted by thesame reference signs throughout the drawings, and repetitivedescriptions will be omitted as necessary for clarity of explanation.

The embodiments described below may be implemented independently or incombination with any another. These embodiments include novelcharacteristics different from one another. Accordingly, theseembodiments contribute to attaining objects or solving problemsdifferent from one another and also contribute to obtaining advantagesdifferent from one another.

The following descriptions on the embodiments mainly focus on an EvolvedPacket System (EPS) that contains LTE and System Architecture Evolution(SAE). However, these embodiments are not limited to being applied tothe EPS and may be applied to other mobile communication networks orsystems such as 3GPP UMTS, 3GPP2 CDMA2000 systems (1×RTT, High RatePacket Data (HRPD)), global system for mobile communications (GSM(trademark))/General packet radio service (GPRS) systems, and WiMAXsystems.

First Embodiment

FIG. 1 shows a configuration example of a radio communication networkaccording to several embodiments including this embodiment. In theexample shown in FIG. 1, the radio communication network includes one ormore radio terminals (i.e., MTC UEs) 1 and a base station (eNB) 2. EachMTC UE 1 is equipped with at least one wireless transceiver and isconfigured to perform cellular communication with the eNB 2. The eNB 2is configured to manage a cell 21 and perform cellular communicationwith the MTC UEs 1 using a cellular communication technology (e.g.,Evolved Universal Terrestrial Radio Access (E-UTRA) technology).

The eNB 2 shown in FIG. 1 may be a Baseband Unit (BBU) used in theCentralized Radio Access Network (C-RAN) architecture. In other words,the eNB 2 shown in FIG. 1 may be a RAN node to be connected to one ormore Remote Radio Heads (RRHs). In some implementations, the eNB 2serving as a BBU takes charge of control-plane processing and digitalbaseband signal processing for the user-plane. On the other hand, eachRRH takes charge of analog Radio Frequency (RF) signal processing (e.g.,frequency conversion and signal amplification). The C-RAN is alsoreferred to as a Cloud RAN. The BBU is also referred to as a RadioEquipment Controller (REC) or a Data Unit (DU). The RRH is also referredto as a Radio Equipment (RE), a Radio Unit (RU), or a Remote Radio Unit(RRU).

In the example shown in FIG. 1, the distance between the eNB 2 and theMTC UE 1A is larger than the distance between the eNB 2 and the MTC UE1B. Accordingly, it is assumed that the MTC UE 1A has a larger pathlossand its radio quality is degraded. Further, the MTC UE 1C is installedinside a structure (e.g., a building) and it is thus assumed that itsradio quality becomes lower than that in a case in which the MTC UE 1Cis installed outdoors. Furthermore, if the capabilities or functions ofthe MTC UEs 1 are limited compared to those of other UEs (e.g.,smartphones and tablet computers) that perform human type communication,such as voice communication and web browsing, it is expected thatdegradation in the radio quality of the MTC UEs 1 will become moreserious. Accordingly, the MTC UEs 1 according to this embodiment supportthe aforementioned coverage enhancement technique.

As already described above, repetition of DL transmission, e.g.,repetitive transmission of system information, M-PDCCH, and PDSCH may beused to improve the downlink (DL) cell coverage. To improve the uplink(UL) cell coverage, repetition of UL transmission, e.g., repetitivetransmission of RACH preamble, PUCCH, and PUSCH may be used.

The MTC UE 1 may support a plurality of CE modes (or ECMs). In someimplementations, the MTC UE 1 may support CE modes (or ECMs) for theRRC_IDLE state and other CE modes (or ECMs) for the RRC_CONNECTED state.Additionally or alternatively, the MTC UE 1 may support either CE modes(or ECMs) for the RRC_IDLE state or CE modes (or ECMs) for theRRC_CONNECTED state. In some implementations, plural coverageenhancement levels are defined per CE mode (or per ECM). Additionally oralternatively, in some implementations, plural CE modes provide pluralcoverage enhancement levels that differ from one another.

FIG. 2 shows an example (Process 200) of an operation of transmittingsystem information according to this embodiment. In Step 201, the eNB 2transmits system information (e.g., SIB1-bis, SIB2-bis) in the cell 21.The eNB 2 may repetitively transmit the system information (SIB1bis,SIB2-bis) in accordance with a coverage enhancement configuration forthe DL of the cell 21.

The system information transmitted in Step 201 contains informationexplicitly or implicitly indicating that the coverage enhancementtechnique (Coverage enhancement solution) is supported in the cell andcontrol information used for the coverage enhancement technique (e.g.,coverage enhancement configuration). In particular, the systeminformation contains a value (hereinafter referred to as a “base value”)of a first radio resource configuration information element (IE). Thisvalue is associated with normal coverage (zero coverage extension) orwith a first coverage enhancement (CE) level (e.g., a CE level 1). Thefirst radio resource configuration IE needs to be set to differentvalues for different CE levels. For example, the first radio resourceconfiguration IE may pertain to at least one of an UL message, an ULphysical channel, a DL message, and a DL physical channel, each of whichis repetitively transmitted in a random access procedure.

In some implementations, the first radio resource configuration IE mayinclude at least one of the following IEs regarding a RACHconfiguration:

-   -   numberOfRA-Preambles;    -   maxNumPreambleAttemptCE;    -   numRepetitionPerPreambleAttempt;    -   ra-ResponseWindowSize;    -   mac-ContentionResolutionTimer;    -   maxHARQ-Msg3Tx; and    -   numRepetitionPerRA-Response.

The “numberOfRA-Preambles” IE indicates the total number of randomaccess preambles (i.e., RACH preambles) available for contention-basedrandom access. The “maxNumPreambleAttemptCE” IE indicates the maximumnumber of PRACH attempts (per CE level). The“numRepetitionPerPreambleAttempt” IE indicates the number of repetitionsof preamble transmission per PRACH attempt (per CE level). The“ra-ResponseWindowSize” IE indicates the duration of a random access(RA) response window. The “mac-ContentionResolutionTimer” IE indicates atimer value of a MAC contention resolution timer to wait for receptionof a Medium Access Control (MAC) Contention Resolution message for RAContention Resolution from the eNB 2 after a third message (Msg3) (i.e.,RRC Connection Request message) in the random access procedure istransmitted to the eNB 2. The “maxHARQ-Msg3Tx” IE indicates the maximumnumber of Hybrid Automatic Repeat Request (HARQ) retransmissions of athird message (Msg3) (i.e., RRC Connection Request message) in therandom access procedure. The “numRepetitionPerRA-Response” IE indicatesthe number of repetitions (per CE level) of M-PDCCH transmission usedfor transmission of a second message (Msg2) (i.e., random accessresponse (RAR) message) in the random access procedure, or indicates thenumber of repetitions of RAR message transmission in the random accessprocedure. The names of these IEs are merely examples and other namesmay be used for these IEs.

FIG. 3 shows an example of the repetitive RACH-preamble transmissionperformed by the MTC UE 1 supporting the coverage enhancement technique.In the example shown in FIG. 3, the MTC UE 1 repeats four preambletransmissions for one PRACH attempt, and performs 20 PRACH attempts atmaximum. If one attempt is failed, the MTC UE 1 increases thetransmission power of an RACH preamble in accordance with the powerramping scheme and starts the next attempt.

FIG. 4 shows an example of values of radio resource configurationinformation elements for plural CE levels. In the example shown in FIG.4, the value of the “maxNumPreambleAttemptCE” IE associated with theminimum CE level (i.e., CE level 1) is 20, and the value of the“numRepetitionPerPreambleAttempt” IE associated with the minimum CElevel (i.e., CE level 1) is 4. This corresponds to the example shown inFIG. 3. On the other hand, in higher CE levels, the maximum number ofPRACH attempts and the number of repetitions of preamble transmissionper PRACH attempt both increase. Specifically, with regard to CE level2, the value of the “maxNumPreambleAttemptCE” IE is 60 and the value ofthe “numRepetitionPerPreambleAttempt” IE is 10. Further, with regard toCE level 3, the value of the “maxNumPreambleAttemptCE” IE is 120 and thevalue of the “numRepetitionPerPreambleAttempt” IE is 20.

In some implementations, the first radio resource configuration IE mayinclude at least one of the following IEs regarding a PRACHconfiguration:

-   -   prach-ConfigIndex; and    -   prach-FreqOffset.

The “prach-ConfigIndex” IE indicates a value (i.e., R_Slot) to definewhen the MTC UE 1 should transmit a random access preamble infrequency/time grids. The “prach-FreqOffset” IE indicates a frequencyoffset value to specify a Physical Resource Block (PRB) available forRACH access.

The 3GPP specification specifies a set of a predetermined number of(e.g., eight) values or a one-dimensional array that can be set in aradio resource configuration IE. These values are arranged in theirascending order or descending order, for example, and each of thesevalues is associated with an index value indicating a rank in theascending order or the descending order. Accordingly, each radioresource configuration IE indicates an index value representing any oneof the values included in the set or the one-dimensional array. Forexample, in the 3GPP Release 12, the RA response window size is in unitof subframes and can have eight different values, i.e., 2, 3, 4, 5, 6,7, 8, or 10 subframes. Accordingly, the “ra-ResponseWindowSize” IE has a3-bit length and indicates one of these eight different values by the3-bit index value.

The MTC UE 1 receives from the eNB 2 the base value of the first radioresource configuration IE associated with the normal coverage (zerocoverage extension, CE level 0) or the first CE level (e.g., CE level1), and then derives from the received base value a value (i.e., thesecond value) of the first radio resource configuration IE associatedwith another CE level (i.e., the second CE level (e.g., CE level 2)).Accordingly, the MTC UE 1 does not need to receive from the eNB 2 anadditional IE that explicitly indicates the second value of the firstradio resource configuration IE associated with the second CE level.

To be more specific, the MTC UE 1 uses a value of a conversion factor toderive the second value associated with the second CE level (e.g., CElevel 2) from the base value received from the eNB 2. The conversionfactor may be simply referred to as a factor. To support the derivationof the second value in the MTC UE 1, in some implementations, the eNB 2may further incorporate the value of the conversion factor into thesystem information transmitted in Step 201 of FIG. 2. Alternatively, insome implementations, the eNB 2 may further incorporate information thatindirectly indicates the value of the conversion factor, or informationto derive the value of the conversion factor, into the systeminformation transmitted in Step 201 of FIG. 2. For example, theinformation that indirectly indicates the value of the conversion factormay be an index that specifies one value from among a set ofpredetermined candidate values. For example, the information to derivethe value of the conversion factor may include one or more parameters tobe substituted into a predetermined formula for calculating theconversion factor. That is, the eNB 2 may transmit, to the MTC UE 1,information about the conversion factor (e.g., the value of theconversion factor itself, information indirectly indicating the value ofthe conversion factor, or information to derive the value of theconversion factor). The information about the conversion factor is usedby the MTC UE 1 to obtain the value of the conversion factor. In thiscase, the conversion factor and the procedure for deriving (orcalculating) the second value using the conversion factor are defined insuch a way that the data size of the information about the conversionfactor is smaller than the data size that is necessary to explicitlytransmit to the MTC UE 1, from the eNB 2, values of one or more radioresource configuration IEs associated with the second CE level.

Prior to Step 201, the eNB 2 may calculate the value of the conversionfactor to be transmitted to the MTC UE 1. Specifically, the eNB 2 maydetermine a value(s) of the first radio resource configuration IE forone or more second CE levels (e.g., CE levels 1-3), and then calculateone or more values of the conversion factor for the one or more secondCE levels using the determined IE value(s) and the base value of thefirst radio resource configuration IE (e.g., the IE value for CE level0).

In another implementation, the MTC UE 1 may store a default value of theconversion factor in its memory in advance, and use the default value toderive the second value from the base value of the first radio resourceconfiguration IE when the conversion factor is not explicitlytransmitted from the eNB 2.

FIG. 5 is a flowchart showing an example (Process 500) of the operationsof the MTC UE 1. In Step 501, the MTC UE 1 receives, from the eNB 2,system information containing the base value of the first radio resourceconfiguration IE. As already described above, the base value of thefirst radio resource configuration IE is the value of the first radioresource configuration IE associated with the normal coverage (i.e.,zero coverage extension) or the first CE level (e.g., CE level 1). Thissystem information may further contain the conversion factor used toderive from the base value the second value of the first radio resourceconfiguration IE associated with the second CE level.

In Step 502, the MTC UE 1 derives the value of the first radio resourceconfiguration IE associated with the second CE level by converting thebase value of the first radio resource configuration IE associated withthe normal coverage (or the first CE level) using the value of theconversion factor. The first radio resource configuration IE includes,for example, one or more RACH configuration IEs (e.g.,ra-ResponseWindowSize and mac-ContentionResolutionTimer). In this case,the MTC UE 1 uses the value of the conversion factor to derive thesecond value(s) associated with the first CE level (or the second CElevel) from the base value(s) of the one or more RACH configuration IEsassociated with the normal coverage (or the first CE level).

The MTC UE 1 may calculate the reference signal received power (RSRP)from the eNB 2 or an estimated pathloss between the MTC UE 1 and the eNB2 and determine, based on the calculated RSRP or pathloss, the CE levelthat is required. In Step 503, if the MTC UE 1 requires the second CElevel, the MTC UE 1 performs the random access procedure in accordancewith the second value(s) of the first radio resource configuration IE(s)derived in Step 502 (e.g., ra-ResponseWindowSize andmac-ContentionResolutionTimer).

The following provides some examples of the conversion factor and someexamples of the procedure for deriving (or calculating) the second valueof the radio resource configuration IE from its base value using theconversion factor. In the first example shown in FIG. 6, the conversionfactor indicates a multiplier factor. Further, in the first example, acommon value of the conversion factor (i.e., multiplier factor) is usedto derive two or more values, associated with the second CE level, oftwo or more radio resource configuration IEs (e.g.,ra-ResponseWindowSize and mac-ContentionResolutionTimer). Accordingly,in the first example, the eNB 2 needs only to transmit a common value ofthe conversion factor instead of transmitting two or more values of thetwo or more radio resource configuration IEs associated with the secondCE level. Accordingly, in the first example, it is possible to reducedata size necessary for a base station to notify a radio terminal of aplurality of radio resource configurations for a plurality of CE levels.The conversion factor in the first example may also be called a scalingfactor, a coefficient, or a scaling coefficient.

To be more specific, in the example shown in FIG. 6, the MTC UE 1receives values of the “ra-ResponseWindowSize” and“mac-ContentionResolutionTimer” IEs for the normal coverage (i.e., zerocoverage extension or CE level 0) from the eNB 2 in the SIB (601). InFIG. 6, the RA response window size (i.e., ra-ResponseWindowSize) forthe normal coverage is 2 subframes (i.e., sf2) and the length of thecontention resolution timer (i.e., mac-ContentionResolutionTimer) forthe normal coverage is 8 subframes (i.e., sf8).

The MTC UE 1 further receives three values of the conversion factor(i.e., multiplier factor) each associated with a respective one of threeCE levels (i.e., CE levels 1, 2, and 3) from the eNB 2 (602). In FIG. 6,the values of the conversion factor (i.e., multiplier factor) for CElevels 1, 2, and 3 are 2, 3, and 4, respectively. Alternatively, the MTCUE 1 may receive from the eNB 2 only one value of the conversion factorcorresponding to one CE level that is necessary among the three CElevels.

The MTC UE 1 multiplies each of the two or more IE values for the normalcoverage (601) by each of the values of the conversion factor(multiplier factor) (603). Accordingly, the MTC UE 1 is able to derivetwo or more values of the two or more IEs for each of CE level 1, 2, and3 (604). The MTC UE 1 may calculate only the values associated with oneCE level that is necessary among the three CE levels.

In the second example shown in FIG. 7, two or more IE values for two ormore CE levels are calculated using a common value of the conversionfactor. Specifically, the MTC UE 1 calculates the third value of theradio resource configuration IE associated with the third CE level, aswell as the second value associated with the second CE level, using thebase value of the radio resource configuration IE and the value of theconversion factor. Accordingly, in the second example, the eNB 2 needsonly to transmit a common value of the conversion factor instead oftransmitting two or more values, associated with the second and third CElevels, of the first radio resource configuration IE. Accordingly, inthe second example, it is possible to reduce data size necessary for abase station to notify a radio terminal of a plurality of radio resourceconfigurations for a plurality of CE levels.

To be more specific, in the example shown in FIG. 7, the MTC UE 1receives a value of the “ra-ResponseWindowSize” IE for the normalcoverage (i.e., zero coverage extension or CE level 0) from the eNB 2 inthe SIB (701). In FIG. 7, the RA response window size (i.e.,ra-ResponseWindowSize) for the normal coverage is 2 subframes (i.e.,sf2).

The MTC UE 1 further receives, from the eNB 2, a common value of theconversion factor (i.e., base multiplier factor) used to obtain three IEvalues for three CE levels (i.e., CE levels 1, 2, and 3) (702). In FIG.7, the value of the conversion factor (i.e., base multiplier factor) is2.

The MTC UE 1 multiplies the value of the radio resource configuration IE(701) for the normal coverage by the value of the conversion factor(i.e., base multiplier factor) (703). Accordingly, the MTC UE 1 is ableto derive the IE value for CE level 1 (704). Further, to obtain the IEvalue for CE level 2, the MTC UE 1 multiplies the IE value for CE level1 by the value of the conversion factor (i.e., base multiplier factor).That is, in the example shown in FIG. 7, the value of the conversionfactor (i.e., base multiplier factor) directly or indirectly specifiesscaling factors of the IE value for the normal coverage to therespective IE values for the two or more CE levels. The MTC UE 1 is thusable to calculate two or more IE values respectively for two or more CElevels based on the common value of the conversion factor (i.e., basemultiplier factor).

In the third example shown in FIG. 8, the conversion factor representsan offset. In the third example, similar to the above-described firstexample, one value of the conversion factor (i.e., offset) is used toderive two or more values, associated with the second CE level, ofrespective two or more radio resource configuration IEs (e.g.,ra-ResponseWindowSize and mac-ContentionResolutionTimer). Accordingly,in the third example, similar to the first example, it is possible toreduce data size necessary for a base station to notify a radio terminalof a plurality of radio resource configurations for a plurality of CElevels.

To be more specific, in the example shown in FIG. 8, the MTC UE 1receives values of the “ra-ResponseWindowSize” and“mac-ContentionResolutionTimer” IEs for the normal coverage (i.e., zerocoverage extension or CE level 0) from the eNB 2 in the SIB (801). InFIG. 8, the RA response window size (i.e., ra-ResponseWindowSize) forthe normal coverage is 2 subframes (i.e., sf2) and the length of thecontention resolution timer for the normal coverage (i.e.,mac-ContentionResolutionTimer) is 8 subframes (i.e., sf8).

The MTC UE 1 further receives three values of the conversion factor(i.e., offset) each associated with a respective one of three CE levels(i.e., CE levels 1, 2, and 3) from the eNB 2 (802). In FIG. 8, thevalues of the conversion factor (i.e., offset) for CE levels 1, 2, and 3are 2, 4, and 6, respectively. Alternatively, the MTC UE 1 may receivefrom the eNB 2 only one value of the conversion factor corresponding toone CE level that is necessary among the three CE levels.

The MTC UE 1 adds the value of the conversion factor (offset) to each ofthe two or more IE values (801) for the normal coverage (803). The MTCUE 1 is thus able to derive two or more values of the two or more IEsfor each of CE level 1, 2, and 3 (804). The MTC UE 1 may calculate onlythe values associated with one CE level that is necessary among thethree CE levels.

In the fourth example shown in FIG. 9, similar to the above-describedsecond example, two or more IE values for two or more CE levels arecalculated using a common value of a conversion factor. Accordingly, inthe fourth example, similar to the second example, it is possible toreduce data size necessary for a base station to notify a radio terminalof a plurality of radio resource configurations for a plurality of CElevels. In the fourth example, a base offset is used as the conversionfactor.

To be more specific, in the example shown in FIG. 9, the MTC UE 1receives a value of the “ra-ResponseWindowSize” IE for the normalcoverage (i.e., zero coverage extension or CE level 0) from the eNB 2 inthe SIB (e.g., SIB2-bis) (901). In FIG. 9, the RA response window size(i.e., ra-ResponseWindowSize) for the normal coverage is 2 subframes(i.e., sf2).

The MTC UE 1 further receives, from the eNB 2, a common value of theconversion factor (i.e., base offset) used to obtain three IE values forthree CE levels (i.e., CE levels 1, 2, and 3) (902). In FIG. 9, thevalue of the conversion factor (i.e., base offset) is 2.

The MTC UE 1 adds the value of the conversion factor (i.e., base offset)to the value (901) of the radio resource configuration IE for the normalcoverage (903). Accordingly, the MTC UE 1 is able to derive the IE valuefor CE level 1 (904). Further, to obtain the IE value for CE level 2,the MTC UE 1 adds the value of the conversion factor (i.e., base offset)to the IE value for CE level 1. That is, in the example shown in FIG. 9,the value of the conversion factor (i.e., base offset) indirectlyspecifies scaling factors of the IE value for the normal coverage to therespective IE values for the two or more CE levels. Accordingly, the MTCUE 1 is able to calculate two or more IE values for two or more CElevels based on a common value of the conversion factor (i.e., baseoffset).

The fifth example is a modified example of the above-described firstexample. In the fifth example, the conversion factor indicates a divisorfactor. In the fifth example, similar to the first example, one value ofthe conversion factor (i.e., divisor factor) is used to derive two ormore values, associated with the second CE level, of respective two ormore radio resource configuration IEs. In some implementations, the MTCUE 1 divides the two or more values of the respective two or more IEsfor the normal coverage by the value of the conversion factor (i.e.,divisor factor) for each CE level. The MTC UE 1 is thus able to derivetwo or more values of the respective two or more IEs for each CE level.The fifth example may be used to obtain a value of an IE (e.g.,maxNumPreambleAttemptCE) that decreases as the CE level becomes higher.

The sixth example is a modified example of the above-described secondexample. In the sixth example, the conversion factor indicates a basedivisor factor. In the sixth example, similar to the second example, twoor more IE values for two or more CE levels are calculated using acommon value of the conversion factor. In some implementations, the MTCUE 1 divides the IE value for the normal coverage by the value of theconversion factor (i.e., base divisor factor). Accordingly, the MTC UE 1is able to calculate two or more IE values for two or more CE levelsbased on a common value of the conversion factor (i.e., base divisorfactor). The sixth example may be used to obtain values of an IE (e.g.,maxNumPreambleAttemptCE) that decreases as the CE level becomes higher.

The seventh example is a modified example of the above-described firstexample. In the seventh example, the conversion factor indicates anexponent of the power of an integer m (i.e., power of m). When theconversion factor is a positive integer k, the second value of a radioresource configuration IE is obtained by multiplying the base value ofthe radio resource configuration IE by the k-th power of m. The value ofthe base “m” of the exponentiation may be defined by the 3GPPspecifications. That is, the value of the base “m” of the exponentiationmay be stored in a memory of the MTC UE 1 in advance. For example, whenthe base “m” is equal to 2 and the value of the conversion factor for CElevel 1 is 3, the value of the radio resource configuration IE for CElevel 1 is obtained by multiplying the base value of the radio resourceconfiguration IE for the normal coverage (i.e., CE level 0) by 2³, i.e.,the value for CE level 1 is eight times as large as the base value. Inthe seventh example, similar to the first example, one value of theconversion factor (i.e., exponent) is used to derive two or more values,associated with the second CE level (e.g., CE level 1), of respectivetwo or more radio resource configuration IEs.

The above-described first to seventh examples may be modified asappropriate. Further, to derive the second value of the radio resourceconfiguration IE from its base value using the conversion factor, amethod other than the methods described in the first to sixth examplesmay be used.

For example, in the first to seventh examples, the value of theconversion factor is a multiplier factor, an offset, a divisor factor,or an exponent of an exponentiation to be used for multiplication,addition, or division of a specific value (e.g., the number ofsubframes) indicated by the base value (i.e., the index value) of theradio resource configuration IE. Alternatively, the value of theconversion factor may be a multiplier factor, an offset, a divisorfactor, or an exponent of an exponentiation to be used formultiplication, addition, or division of the base value itself (i.e.,the index value) of the radio resource configuration IE. For example,the base value itself (i.e., the index value) of the radio resourceconfiguration IE may be multiplied by the value of the multiplierfactor, which is the conversion factor. In this case, a specific valueindicated by the converted index value (e.g., the number of subframes)is used for the corresponding CE level.

The above-described first to seventh examples may be combined asappropriate. For example, when values of respective IEs are calculatedusing a common conversion factor, the role of the conversion factor(i.e., the calculation method for deriving an IE value) may be differentfor each IE. For example, the value of the conversion factor may be usedas a multiplier factor for multiplication to obtain a value of one IE,and meanwhile the value of the conversion factor may be used as anoffset for addition to obtain a value of another IE.

In some implementations, the value of the conversion factor, which isused to obtain a value of the first radio resource configuration IEassociated with the second CE level, may also be used as a value,associated with the second coverage enhancement level, of a second radioresource configuration IE different from the first radio resourceconfiguration IE. For example, the MTC UE 1 may use one or both of thevalue of the “numRepetitionPerPreambleAttempt” IE indicating the numberof preamble repetitions (i.e., PRACH preamble repetition level) in thesecond CE level received from the eNB 2 and the value of the“numRepetitionPerRA-Response” IE indicating the number of RA responserepetitions (i.e., RAR repetition level) in the second CE level receivedfrom the eNB 2 as the conversion factor(s) to obtain values of the“ra-ResponseWindowSize” and “mac-ContentionResolutionTimer” IEsassociated with the second CE level. Additionally or alternatively, theMTC UE 1 may use one or both of the value of the IE indicating therepetition level (i.e., the number of repetitions) of the third message(i.e., RRC Connection Request message) in the random access procedure inthe second CE level received from the eNB 2 and the value of the IEindicating the repetition level (the number of repetitions) of thefourth message (i.e., Contention Resolution message) in the second CElevel received from the eNB 2 as the conversion factor(s) to obtain avalue of the “mac-ContentionResolutionTimer” IE associated with thesecond CE level. In these two examples, the coefficient (proportionalcoefficient) that associates one or both of the PRACH preamblerepetition level and the RAR repetition level with thera-ResponseWindowSize may be the same as the coefficient (proportionalcoefficient) that associates one or both of the repetition level of thethird message and the repetition level of the fourth message with themac-ContentionResolutionTimer.

In some implementations, to obtain an IE value corresponding to thenecessary CE level in the MTC UE 1, the MTC UE 1 uses another factor inaddition to the conversion factor. For example, the MTC UE 1 derives anIE value using the repetition level (i.e., the number of repetitions) ofthe corresponding signal (e.g., preamble, message) and the conversionfactor. For example, the MTC UE 1 may derive the value of thera-ResponseWindowSize for the second CE level by multiplying the valueof the ra-ResponseWindowSize for the first CE level (e.g., CE level 0)by the value of the PRACH preamble repetition level for the second CElevel (e.g., CE level 1, 2, or 3) and further multiplying (or adding ordividing) the resulting value by (or to) the value of the conversionfactor. In this case, the value of the conversion factor may be a valueindicating the interval of two repetitive transmissions of the RACHpreamble, or a value indicating the interval between two repetitivetransmissions of the RAR message (e.g., M-PDCCH or PDSCH).

Further, when a common conversion factor is used for a plurality of IEs,the MTC UE 1 may derive a value of each IE using the repetition level(i.e., the number of repetitions) of its corresponding signal (i.e.,preamble or message) and the common conversion factor. For example, theMTC UE 1 may derive the value of the ra-ResponseWindowSize for thesecond CE level (e.g., CE level 1, 2, or 3) by multiplying the value ofthe ra-ResponseWindowSize for the first CE level (e.g., CE level 0) bythe value of the PRACH preamble repetition level or the RAR repetitionlevel for the second CE level and further multiplying (or adding ordividing) the resulting value by (or to) the value of the conversionfactor. In a similar way, the MTC UE 1 may derive the value of themac-ContentioResolutionTimer for the second CE level (e.g., CE level 1,2, or 3) by multiplying the value of the mac-ContentioResolutionTimerfor the first CE level (e.g., CE level 0) by one or both of the valuesof the repetition level of the third message (i.e., RRC ConnectionRequest message) and the repetition level of the fourth message (i.e.,Contention Resolution message) for the second CE level and furthermultiplying (or adding or dividing) the resulting value by the commonconversion factor.

In some implementations, the value of the conversion factor may be a CElevel value. For example, the value of the conversion factor may be avalue (e.g., 1) indicating the CE level (e.g., CE level 1) that isnecessary, or may be a value obtained by converting the value indicatingthe CE level in accordance with a predetermined conversion equation.

In some implementations, the derivation of an IE value(s) using theconversion factor may be performed only for one (or a few) CE levels(e.g., CE level 1) of the plurality of CE levels, and an IE value(s) forthe remaining CE level(s) (e.g., CE level 1 and CE level 2) may bederived from the IE value(s) for the one (or a few) CE levels (e.g., CElevel 1) in accordance with a predetermined rule. For example, the IEvalue for CE level 2 may be twice as large as the IE value for CE level1 and the IE value for CE level 3 may be three times as large as the IEvalue for CE level 1. Alternatively, the IE value for CE level 2 may bea value obtained by adding “offset+2” to the IE value for CE level 1 andthe IE value for CE level 3 may be a value obtained by adding “offset+3”to the IE value for CE level 1. Alternatively, the IE values may bederived using a value corresponding to the difference (e.g., the ratioor the difference) in repetition level (i.e., the number of repetitions)between CE levels. For example, when the repetition level for CE level 1is 2 and the repetition level for CE level 2 is 4, the IE value for CElevel 2 may be set to a value 4/2 times as large as the IE value for CElevel 1, i.e., a value twice as large as the IE value for CE level 1.

The above-described first, third, fifth, and seventh examples providethe examples in which one value of the conversion factor is configured(or used) in common for two or more radio resource configuration IEs. Onthe other hand, the second, fourth, and sixth examples provide theexamples in which one value of the conversion factor is configured (orused) in common for two or more CE levels. Alternatively, in someimplementations, one value of the conversion factor may be configured(or used) per radio resource configuration IE and per CE level. In thiscase, the conversion factor is preferably defined in such a manner thatthe bit length of the IE indicating the conversion factor is smallerthan the bit length of the radio resource configuration IE.

FIG. 10 is a diagram showing an example (Process 1000) of the randomaccess procedure according to this embodiment. In Step 1001, the MTC UE1 determines (estimates) the CE level that is necessary based on ameasured value of reception quality (e.g., RSRP) of a signal from theeNB 2 or a measured value (estimated value) of pathloss between the UE 1and the eNB 2.

In Step 1002, the MTC UE 1 receives system information (SIB) transmittedfrom the eNB 2 while using the coverage enhancement technique (e.g.,repetitive transmission of the system information (SIB)) correspondingto the determined CE level. This system information contains the basevalue of the first radio resource configuration IE (e.g., one or moreRACH configuration IEs) associated with the normal coverage or the firstCE level (e.g., CE level 1) and further contains the information aboutthe conversion factor to derive the value of the first radio resourceconfiguration IE associated with the second CE level (e.g., CE level 2).As already described above, for example, the information about theconversion factor may include the value of the conversion factor itself,or it may be information indirectly indicating the value of theconversion factor or information for deriving the value of theconversion factor.

In Step 1003, the MTC UE 1 converts the base value of the first radioresource configuration IE associated with the normal coverage (or thefirst CE level) using the value of the conversion factor. The value ofthe conversion factor can be obtained from the information about theconversion factor received from the eNB 2. The MTC UE 1 thus derives thevalue of the first radio resource configuration IE associated with thedetermined CE level.

After that, the MTC UE 1 performs the random access procedure inaccordance with the derived value of the first radio resourceconfiguration IE (e.g., one or more RACH configuration IEs) (Steps1004-1006).

In Step 1004, if the MTC UE 1 has not successfully completed the randomaccess even after the number of RACH preamble attempts reaches themaximum number with respect to the determined (estimated) CE level(e.g., CE level 1), the MTC UE 1 may start RACH preamble transmissionusing the configuration for the next CE level (e.g., CE level 2). Inthis case, the MTC UE 1 may derive the configuration for the next CElevel (e.g., CE level 2), such as the values of the“ra-ResponseWindowSize” and “mac-ContentionResolutionTimer” IEs, whenthe applied CE level is changed, or it may collectively derive thevalues each associated with respective CE levels, in advance.

The MTC UE 1 may start the RA response window, in accordance with the“ra-ResponseWindowSize” IE, at the third subframe subsequent to thebeginning or the end of the repetitive transmissions within one RACHpreamble transmission attempt in Step 1004. The “ra-ResponseWindowSize”IE indicates the time that the MTC UE 1 should wait for reception ofrandom access response (RAR) in Step 1006 after it has transmitted theRACH preamble in Step 1004. Further, the MTC UE 1 may start the MACcontention resolution timer, in accordance with the“mac-ContentionResolutionTimer” IE, after the beginning or the end ofthe repetitive third message (Msg3) transmissions in the random accessprocedure. The “mac-ContentionResolutionTimer” IE indicates the timethat the MTC UE 1 should wait for reception of a Contention Resolutionmessage (check of the content) after it has transmitted the thirdmessage (Msg3).

In Step 1005, the eNB 2 detects the random access (RA) preamble (i.e.,RACH preamble) transmitted from the MTC UE 1. For example, the eNB 2determines the CE level of the MTC UE 1 based on the radio resource onwhich the RA preamble has been detected. Then the eNB 2 performs anoperation for the coverage enhancement, including the repetitivereception of the RA preamble and the repetitive transmission of the RAresponse, in accordance with the values of a plurality of IEs (e.g.,“numRepetitionPerPreambleAttempt” and “ra-ResponseWindowSize” IE)corresponding to the CE level determined for the MTC UE 1. In someimplementations, the eNB 2 may calculate the values of the plurality ofIEs corresponding to the CE level determined for the MTC UE 1 based onthe value of the conversion factor for this CE level. In some otherimplementations, the eNB 2 may calculate the values of the plurality ofIEs corresponding to the CE level determined for the MTC UE 1 byreferring to a lookup table that stores the values of each IEcorresponding to respective CE levels.

The above-described specific example provides methods of derivingvalues, each associated with respective CE levels, of an existing radioparameter regarding the random access procedure (i.e., an IE in RRCmessages). In a similar way, the above-described deriving method may beused to derive values, each associated with respective CE levels, of aradio parameter (i.e., an IE in RRC messages) that is newly defined forthe coverage enhancement technique. For example, the above-describedderiving methods may be applied to the IE indicating the maximum numberof RACH preamble attempts per CE level (i.e., maxNumPreambleAttemptCE)and the IE indicating the maximum number of repetitions per RACHpreamble attempt (i.e., numRepetitionPerPreambleAttempt). In this case,the eNB 2 may transmit the IE values corresponding to the lowest CElevel (e.g., CE level 1) by the system information, and the UE 1 mayderive the IE values corresponding to one or more higher CE levels(e.g., CE level 2 or a CE level higher than CE level 2) using theabove-described conversion factor.

The above-described random access procedure may be applied not only toan initial access when the UE is switched from the RRC_IDLE state to theRRC_CONNECTED state but also to a random access in the RRC_CONNECTEDstate. Further, when a random access is performed in response to aninstruction (i.e., PDCCH Order) from the eNB 2, this instruction mayinclude at least one of the base value and the conversion factor.

The following provides configuration examples of the MTC UE 1 and theeNB 2 according to this embodiment. FIG. 11 is a block diagram showing aconfiguration example of the MTC UE 1. A Radio Frequency (RF)transceiver 1101 performs analog RF signal processing to communicatewith the eNB 2. The analog RF signal processing performed by the RFtransceiver 1101 includes frequency up-conversion, frequencydown-conversion, and amplification. The RF transceiver 1101 is coupledto an antenna 1102 and a baseband processor 1103. That is, the RFtransceiver 1101 receives modulated symbol data (or OFDM symbol data)from the baseband processor 1103, generates a transmission RF signal,and supplies the transmission RF signal to the antenna 1102. Further,the RF transceiver 1101 generates a baseband reception signal based on areception RF signal received by the antenna 1102, and supplies thebaseband reception signal to the baseband processor 1103.

The baseband processor 1103 performs digital baseband signal processing(i.e., data plane processing) and control plane processing for radiocommunication. The digital baseband signal processing includes (a) datacompression/decompression, (b) data segmentation/concatenation, (c)composition/decomposition of a transmission format (i.e., transmissionframe), (d) channel coding/decoding, (e) modulation (i.e., symbolmapping)/demodulation, and (f) generation of OFDM symbol data (i.e.,baseband OFDM signal) by Inverse Fast Fourier Transform (IFFT). On theother hand, the control plane processing includes communicationmanagement of layer 1 (e.g., transmission power control), layer 2 (e.g.,radio resource management and hybrid automatic repeat request (HARQ)processing), and layer 3 (e.g., signalling regarding attach, mobility,and packet communication).

In the case of LTE and LTE-Advanced, for example, the digital basebandsignal processing performed by the baseband processor 1103 may includesignal processing of a Packet Data Convergence Protocol (PDCP) layer, aRadio Link Control (RLC) layer, the MAC layer, and the PHY layer.Further, the control plane processing performed by the basebandprocessor 1103 may include processing of a Non-Access Stratum (NAS)protocol, an RRC protocol, and MAC CEs.

The baseband processor 1103 may include a modem processor (e.g., aDigital Signal Processor (DSP)) that performs the digital basebandsignal processing and a protocol stack processor (e.g., a CentralProcessing Unit (CPU) or a Micro Processing Unit (MPU)) that performsthe control plane processing. In this case, the protocol stackprocessor, which performs the control plane processing, may beintegrated with an application processor 1104 described in thefollowing.

The application processor 1104 is also referred to as a CPU, an MPU, amicroprocessor, or a processor core. The application processor 1104 mayinclude a plurality of processors (processor cores). The applicationprocessor 1104 executes a system software program (Operating System(OS)) and various application programs (e.g., communication applicationto acquire metering data or sensing data) loaded from a memory 1106 orfrom another memory (not shown), thereby providing various functions ofthe MTC UE 1.

In some implementations, as represented by a dashed line (1105) in FIG.11, the baseband processor 1103 and the application processor 1104 maybe integrated on a single chip. In other words, the baseband processor1103 and the application processor 1104 may be implemented in a singleSystem on Chip (SoC) device 1105. An SoC device may be referred to as asystem Large Scale Integration (LSI) or a chipset.

The memory 1106 is a volatile memory, a non-volatile memory, or acombination thereof. The memory 1106 may include a plurality of memorydevices that are physically independent from each other. The volatilememory is, for example, a Static Random Access Memory (SRAM), a DynamicRAM (DRAM), or a combination thereof. The non-volatile memory is, forexample, a Mask Read Only Memory (MROM), an Electrically ErasableProgrammable ROM (EEPROM), a flash memory, a hard disc drive, or anycombination thereof. The memory 1106 may include, for example, anexternal memory device that can be accessed from the baseband processor1103, the application processor 1104, and the SoC 1105. The memory 1106may include an internal memory device that is integrated in the basebandprocessor 1103, the application processor 1104, or the SoC 1105.Further, the memory 1106 may include a memory in a Universal IntegratedCircuit Card (UICC).

The memory 1106 may store one or more software modules (computerprograms) 1107 including instructions and data to perform processing bythe MTC UE 1 described in the above embodiments. In someimplementations, the baseband processor 1103 or the applicationprocessor 1104 may load the software modules 1107 from the memory 1106and execute the loaded software modules, thereby performing theprocessing of the MTC UE 1 described in the above embodiments.

FIG. 12 is a block diagram showing a configuration example of the basestation (eNB) 2 according to the above-described embodiments. Referringto FIG. 12, the eNB 2 includes an RF transceiver 1201, a networkinterface 1203, a processor 1204, and a memory 1205. The RF transceiver1201 performs analog RF signal processing to communicate with the radioterminal 1. The RF transceiver 1201 may include a plurality oftransceivers. The RF transceiver 1201 is coupled to an antenna 1202 andthe processor 1204. The RF transceiver 1201 receives modulated symboldata (or OFDM symbol data) from the processor 1204, generates atransmission RF signal, and supplies the transmission RF signal to theantenna 1202. Further, the RF transceiver 1201 generates a basebandreception signal based on a reception RF signal received by the antenna1202 and supplies the baseband reception signal to the processor 1204.

The network interface 1203 is used to communicate with the network node(e.g., Mobility Management Entity (MME) and Serving Gateway (S-GW)). Thenetwork interface 1203 may include, for example, a network interfacecard (NIC) conforming to the IEEE 802.3 series.

The processor 1204 performs digital baseband signal processing (dataplane processing) and control plane processing for radio communication.In the case of LTE and LTE-Advanced, for example, the digital basebandsignal processing performed by the processor 1204 may include signalprocessing of a PDCP layer, an RLC layer, a MAC layer, and a PHY layer.Further, the control plane processing performed by the processor 1204may include processing of an S1 protocol, an RRC protocol, and MAC CEs.

The processor 1204 may include a plurality of processors. The processor1204 may include, for example, a modem processor (e.g., a DSP) thatperforms the digital baseband signal processing and a protocol stackprocessor (e.g., a CPU or an MPU) that performs the control planeprocessing.

The memory 1205 is composed of a combination of a volatile memory and anon-volatile memory. The volatile memory is, for example, an SRAM, aDRAM, or a combination thereof. The non-volatile memory is, for example,an MROM, a PROM, a flash memory, a hard disc drive, or any combinationthereof. The memory 1205 may include a storage that is located away fromthe processor 1204. In this case, the processor 1204 may access thememory 1205 via the network interface 1203 or an I/O interface (notshown).

The memory 1205 may store software modules (computer programs) 1206including instructions and data to perform the processing by the eNB 2described in the above embodiments. In some implementations, theprocessor 1204 may load the software modules 1206 from the memory 1205and execute the loaded software modules, thereby performing theprocessing of the eNB 2 described in the above embodiments.

As described above with reference to FIGS. 11 and 12, each of theprocessors included in the MTC UE 1 and the eNB 2 according to theabove-described embodiments executes one or more programs includinginstructions to cause a computer to perform an algorithm described withreference to the drawings. The program(s) can be stored and provided toa computer using any type of non-transitory computer readable media.Non-transitory computer readable media include any type of tangiblestorage media. Examples of non-transitory computer readable mediainclude magnetic storage media (such as flexible disks, magnetic tapes,hard disk drives, etc.), optical magnetic storage media (e.g.,magneto-optical disks), Compact Disc Read Only Memory (CD-ROM), CD-R,CD-R/W, and semiconductor memories (such as mask ROM, Programmable ROM(PROM), Erasable PROM (EPROM), flash ROM, Random Access Memory (RAM),etc.). The program(s) may be provided to a computer using any type oftransitory computer readable media. Examples of transitory computerreadable media include electric signals, optical signals, andelectromagnetic waves. Transitory computer readable media can providethe program to a computer via a wired communication line (e.g., electricwires, and optical fibers) or a wireless communication line.

Other Embodiments

The above embodiments have been described with regard to radio resourceconfiguration IEs regarding random access (e.g., RACH configuration IEand PRACH configuration IE). However, the methods of deriving a IE valuefor a specific CE level using the conversion factor described in theabove embodiments may be widely used for other applications in whichdifferent radio resource configurations for different coverageenhancement (CE) levels are required. The methods described in the aboveembodiments may be used, for example, to derive values of radio resourceconfiguration IEs (e.g., the number of repetitions of transmission (orreception)) required when the MTC UE 1 in the RRC_CONNECTED stateperforms UL user data transmission on PUSCH, transmission of L1/L2control information on PUCCH, reception of system information or DL userdata on PDSCH, and reception of L1/L2 control information on M-PDCCH,using a specific CE level.

The above embodiments have been described with regard to the case inwhich the eNB 2 transmits the information about the conversion factor bythe system information. However, the information about the conversionfactor may be transmitted by a signal (e.g., RRC signaling, MACsignaling) that is used the eNB 2 to transmit dedicated controlinformation to the MTC UE 1. For example, the information about theconversion factor may be transmitted from the eNB 2 to the MTC UE 1 byan RRC Connection Reconfiguration message or a MAC Control Element. Whenthe MTC UE 1 has received the information about the conversion factor inboth the system information and the dedicated control information, theMTC UE 1 may preferentially use the value of the conversion factorobtained from the information about the conversion factor received inthe dedicated control information (i.e., overwrite the value of theconversion factor obtained from the system information by that obtainedfrom the dedicated control information).

The operations of the MTC UE 1 and the eNB 2 regarding the derivation ofIE values using the conversion factor, described in the aboveembodiments, may be used to derive values of a timer that uses differenttimer lengths depending on the coverage enhancement (CE) level. Specificexamples of a timer that uses different timer values for different CElevels include, for example, (1) a timer associated with control (i.e.,RRC, NAS) of call processing etc., (2) a timer associated with Layer 2(i.e., PDCP, RLC, MAC) control, and (3) a timer used in the RRC_IDLEstate.

For example, the aforementioned timer (1) may be a timer (i.e., timerT300) that is used to determine success or failure of an RRC connectionestablishment. The MTC UE 1 starts the timer (i.e., the timer T300) upontransmitting an RRC Connection Reestablishment Request message and stopsthe timer upon receiving a response from the eNB 2 (i.e., RRC ConnectionSetup message or RRC Connection Reject message).

Additionally or alternatively, the aforementioned timer (1) may be atimer (i.e., timer T311) that is used to determine success or failure ofdetection of a suitable cell. The MTC UE 1 starts the timer (i.e., timerT311) upon starting an RRC Connection Reestablishment procedure andstops the timer upon detecting (or selecting) a suitable cell.

Additionally or alternatively, the aforementioned timer (1) may be atimer (i.e., timer T304) that is used to determine success or failure ofa handover. The MTC UE 1 starts the timer (i.e., timer T304) uponreceiving an RRC Connection Reconfiguration message including aMobilityControlInfo IE (that is, the message that instructs thehandover) and stops the timer upon successfully completing a randomaccess procedure to the target cell.

For example, the aforementioned timer (2) may be a timer that is usedfor control in the MAC layer. Specific examples of the timer used forcontrol in the MAC layer include: timers (e.g., OnDurationTimer,drx-InactivityTimer, drx-RetransmissionTimer, HART RTT Timer) related todiscontinuous reception control (Discontinuous Reception (DRX)) in a UE;timers (e.g., sr-ProhibitTimer, logicalChannelSR-ProhibitTimer) formeasuring a period of time during which transmission of SchedulingRequests (SRs) is prohibited; a timer (e.g., PeriodicBSR-Timer,RetxBSR-Timer) related to reporting of an uplink buffer amount (i.e.,Buffer Status Report (BSR)), and a timer (e.g., periodicPHR-Timer,prohibitPHR-Timer) related to reporting of the remaining amount ofuplink transmission power (Power Headroom Report (PHR)).

Additionally or alternatively, the aforementioned timer (2) may be atimer that is used for control in the RLC layer. Specific examples ofthe timer used for control in the RLC layer include a timer (e.g.,T-Reordering) used to detect loss of RLC PDUs and to perform ordercontrol in DL data reception, and a timer (e.g., T-StatusProhibit) formeasuring a period of time during which transmission of informationabout the status of DL data reception (i.e., STATUS PDUs) is prohibited.

Additionally or alternatively, the aforementioned timer (2) may be atimer used for control in the PDCP layer. Specific examples of the timerused for control in the PDCP layer include a timer (e.g., discardTimer)for determining whether to discard pending data in the UL datatransmission.

For example, the aforementioned timer (3) may be a timer used in a cellreselection process performed by the MTC UE 1 in the RRC_IDLE state.Specifically, the aforementioned timer (3) may be a timer for measuringa duration of time during which a condition to trigger the cellreselection is satisfied (i.e., T-Reselection).

The above-described timers may be started from the first or lasttransmission of a repetitive transmission of a signal (or message) thatrelates to (or serves as a trigger for) the respective timers.Alternatively, these timers may be started from the first or lasttransmission of a repetitive reception of a signal (message) thatrelates to (or serves as a trigger for) the respective timers.

In the above-described embodiments, the radio terminal 1 may be anon-MTC UE. That is, the above-described embodiments may be broadlyapplied to communication between a UE and an eNB that support thecoverage enhancement technique including repetitive transmission (orreception).

Further, the above-described embodiments may be applied not only to LTE,LTE-Advanced and modifications thereof but also to communication betweenthe radio terminal and the base station that support the coverageenhancement technique in other radio communication networks or systems.

For example, the above-described embodiments may be applied to thecoverage enhancement technique in the system called Narrow Band-Internetof Things (NB-IoT), which has been discussed in the 3GPP. NB-IoT aims toaccommodate IoT devices having characteristics of low cost and ultra-lowpower consumption (e.g., terminals can operate for ten years withoutexchanging their batteries) in the cellular network. The objects and thecharacteristics of devices in NB-IoT are extremely similar to those inRel-13 MTC, and it has been discussed to reuse the 3GPP Release 13(Rel-13) MTC technologies for NB-IoT. Accordingly, the above-describedembodiments may be applied to NB-IoT. While a Rel-13 MTC UE transmits aRACH preamble in random access, it has been discussed that a NB-IoT UEtransmits a message (e.g., contention-based message), in place of apreamble, on a PRACH. As described above, while it has been discussed tomodify Rel-13 MTCs for NB-IoT or introduce new functions into NB-IoT,the above-described embodiments may be applied to NB-IoT regardless ofdifferences between them.

Further, the above-described embodiments are merely examples regardingapplication of the technical ideas obtained by the present inventor.Needless to say, these technical ideas are not limited to theabove-described embodiments and various modifications can be madethereto.

For example, the whole or part of the above embodiments can be describedas, but not limited to, the following supplementary notes.

(Supplementary Note A1)

A base station comprising:

a memory; and

at least one processor coupled to the memory and configured to transmitto a radio terminal a first value of a first radio resourceconfiguration information element and information about a conversionfactor, the first value being associated with normal coverage or with afirst coverage enhancement level, wherein

a value of the conversion factor obtained from the information about theconversion factor is used by the radio terminal to derive a second valueof the first radio resource configuration information element, thesecond value being associated with a second coverage enhancement level.

(Supplementary Note A2)

The base station according to Supplementary Note A1, wherein

the first radio resource configuration information element comprises twoor more radio resource configuration information elements,

the second value comprises two or more values of the two or more radioresource configuration information elements, the two or more valuesbeing associated with the second coverage enhancement level, and

the value of the conversion factor is used by the radio terminal toderive each of the two or more values from the first value.

(Supplementary Note A3)

The base station according to Supplementary Note A1, wherein the valueof the conversion factor is used by the radio terminal to derive, inaddition to the second value, a third value of the first radio resourceconfiguration information element from the first value, the third valuebeing associated with a third coverage enhancement level.

(Supplementary Note A4)

The base station according to Supplementary Note A3, wherein the valueof the conversion factor directly or indirectly specifies scalingfactors among the first, second, and third values.

(Supplementary Note A5)

The base station according to any one of Supplementary Notes A1 to A4,wherein

the value of the conversion factor comprises a value of a multiplierfactor, and

the second value is calculated by multiplying the first value by thevalue of the multiplier factor.

(Supplementary Note A6)

The base station according to any one of Supplementary Notes A1 to A4,wherein

the value of the conversion factor comprises an offset value, and

the second value is calculated by adding the offset value to the firstvalue.

(Supplementary Note A7)

The base station according to any one of Supplementary Notes A1 to A4,wherein the value of the conversion factor is also used to derive avalue of a second radio resource configuration information elementdifferent from the first radio resource configuration informationelement, the value of the second radio resource configurationinformation element being associated with the second coverageenhancement level.

(Supplementary Note A8)

The base station according to any one of Supplementary Notes A1 to A7,wherein

the first radio resource configuration information element comprises atleast one parameter regarding a random access procedure, and

the at least one parameter comprises at least one of: (a) a parameterthat defines frequency and time resources available for transmission ofa random access preamble; (b) a parameter indicating the total number ofrandom access preambles; (c) a parameter indicating the maximum numberof attempts of a random access preamble; (d) the number of repetitionsof random access preamble transmission for each transmission attempt ofa random access preamble; (e) a parameter indicating a duration of arandom access response window; (f) a parameter indicating a duration ofa contention resolution timer; (g) the maximum number of repetitions ofrandom access response transmission by the base station; and (h) aparameter indicating the maximum number of re-transmissions of a thirdmessage responsive to reception of a random access response.

(Supplementary Note A9)

The base station according to any one of Supplementary Notes A1 to A8,wherein the at least one processor is further configured to:

calculate the value of the conversion factor to be transmitted to theradio terminal using the first and second values; and

transmit the calculated value of the conversion factor to the radioterminal.

(Supplementary Note B1)

A radio terminal comprising:

a memory; and

at least one processor coupled to the memory and configured to executeat least one module comprising:

-   -   a reception module configured to receive from a base station a        first value of a first radio resource configuration information        element, the first value being associated with normal coverage        or a first coverage enhancement level; and    -   a calculation module configured to derive a second value of the        first radio resource configuration information element by        converting the first value using a value of a conversion factor,        the second value being associated with a second coverage        enhancement level.        (Supplementary Note B2)

The radio terminal according to Supplementary Note B1, wherein

the first radio resource configuration information element comprises twoor more radio resource configuration information elements,

the second value comprises two or more values of the two or more radioresource configuration information elements, the two or more valuesbeing associated with the second coverage enhancement level, and

the calculation module is configured to use the value of the conversionfactor to derive each of the two or more values from the first value.

(Supplementary Note B3)

The radio terminal according to Supplementary Note B1, wherein thecalculation module is configured to use the value of the conversionfactor to derive, in addition to the second value, a third value of thefirst radio resource configuration information element from the firstvalue, the third value being associated with a third coverageenhancement level.

(Supplementary Note B4)

The radio terminal according to Supplementary Note B3, wherein the valueof the conversion factor directly or indirectly specifies scalingfactors among the first, second, and third values.

(Supplementary Note B5)

The radio terminal according to any one of Supplementary Notes B1 to B4,wherein the at least one processor is further configured to receive,from the base station, information about the conversion factor to obtainthe value of the conversion factor.

(Supplementary Note B6)

The radio terminal according to any one of Supplementary Notes B1 to B5,wherein

the value of the conversion factor comprises a value of a multiplierfactor, and

the second value is calculated by multiplying the first value by thevalue of the multiplier factor.

(Supplementary Note B7)

The radio terminal according to any one of Supplementary Notes B1 to B5,wherein

the value of the conversion factor comprises an offset value, and

the second value is calculated by adding the offset value to the firstvalue.

(Supplementary Note B8)

The radio terminal according to Supplementary Note B5, wherein the valueof the conversion factor is also used to derive a value of a secondradio resource configuration information element different from thefirst radio resource configuration information element, the value of thesecond radio resource configuration information element being associatedwith the second coverage enhancement level.

(Supplementary Note B9)

The radio terminal according to any one of Supplementary Notes B1 to B8,wherein

the at least one module further comprises:

-   -   an estimation module configured to estimate a coverage        enhancement level with which the radio terminal should comply;        and    -   a communication module configured to communicate with the base        station in accordance with the value of the first radio resource        configuration information element associated with the estimated        coverage enhancement level, and

the calculation module is configured to calculate the second value asthe value of the first radio resource configuration information elementassociated with the estimated coverage enhancement level.

(Supplementary Note B10)

The radio terminal according to any one of Supplementary Notes B1 to B9,wherein

the first radio resource configuration information element comprises atleast one parameter regarding a random access procedure, and

the at least one parameter comprises at least one of: (a) a parameterthat defines frequency and time resources available for transmission ofa random access preamble; (b) a parameter indicating the total number ofrandom access preambles; (c) a parameter indicating the maximum numberof attempts of a random access preamble; (d) the number of repetitionsof random access preamble transmission for each transmission attempt ofa random access preamble; (e) a parameter indicating a duration of arandom access response window; (f) a parameter indicating a duration ofa contention resolution timer; (g) the maximum number of repetitions ofrandom access response transmission by the base station; and (h) aparameter indicating the maximum number of re-transmissions of a thirdmessage responsive to reception of a random access response.

This application is based upon and claims the benefit of priority fromJapanese Patent Application No. 2015-217963, filed on Nov. 5, 2015, thedisclosure of which is incorporated herein in its entirety by reference.

REFERENCE SIGNS LIST

-   1 RADIO TERMINAL (UE)-   2 BASE STATION (eNB)-   1101 RADIO FREQUENCY (RF) TRANSCEIVER-   1103 BASEBAND PROCESSOR-   1104 APPLICATION PROCESSOR-   1106 MEMORY-   1201 RF TRANSCEIVER-   1204 PROCESSOR-   1205 MEMORY

The invention claimed is:
 1. A base station comprising: a memory; and atleast one processor coupled to the memory and configured to: broadcastsystem information, the system information including a first base valueof a random access response window size, a second base value of a MediumAccess Control (MAC) contention resolution timer, and multiplier factorscorresponding to respective coverage enhancement levels; receive arandom access preamble, from a User Equipment (UE) which performs radiocommunication according to Narrow Band-Internet of Things (NB-IoT)corresponding to a coverage enhancement level that is determined by theUE according to Reference Signals Received Power (RSRP) measured by theUE; control transmission of a random access response message based onduration of the random access response window size that is derived bymultiplying the first base value of the random access response windowsize with a multiplier factor corresponding to the coverage enhancementlevel of the UE; and control transmission of a MAC contention resolutionmessage based on duration indicated by a timer value of the MACcontention resolution timer that is derived by multiplying the secondbase value of the MAC contention resolution timer with the multiplierfactor corresponding to the coverage enhancement level, wherein themultiplier factors are values of an information element of a radioresource configuration that is different from the random access responsewindow size and from the MAC contention resolution timer, wherein thevalues of the information element are used for indicating a number ofrepetitions for third and fourth messages of a random access procedure,and wherein the fourth message is the MAC contention resolution message.2. A method in a base station, the method comprising: broadcastingsystem information, the system information including a first base valueof a random access response window size, a second base value of a MediumAccess Control (MAC) contention resolution timer, and multiplier factorscorresponding to respective coverage enhancement levels; receiving arandom access preamble, from a User Equipment (UE) which performs radiocommunication according to Narrow Band-Internet of Things (NB-IoT)corresponding to a coverage enhancement level that is determined by theUE according to Reference Signals Received Power (RSRP) measured by theUE; controlling transmission of a random access response message basedon duration of the random access response window size that is derived bymultiplying the first base value of the random access response windowsize with a multiplier factor corresponding to the coverage enhancementlevel of the UE; and controlling transmission of a MAC contentionresolution message based on duration indicated by a timer value of theMAC contention resolution timer that is derived by multiplying thesecond base value of the MAC contention resolution timer with themultiplier factor corresponding to the coverage enhancement level,wherein the multiplier factors are values of an information element of aradio resource configuration that is different from the random accessresponse window size and from the MAC contention resolution timer,wherein the values of the information element are used for indicating anumber of repetitions for third and fourth messages of a random accessprocedure, and wherein the fourth message is the MAC contentionresolution message.
 3. A non-transitory computer readable medium storinga program for causing a computer to perform a method in a base station,wherein the method comprises: broadcasting system information, thesystem information including a first base value of a random accessresponse window size, a second base value of a Medium Access Control(MAC) contention resolution timer, and multiplier factors correspondingto respective coverage enhancement levels; receiving a random accesspreamble, from a User Equipment (UE) which performs radio communicationaccording to Narrow Band-Internet of Things (NB-IoT) corresponding to acoverage enhancement level that is determined by the UE according toReference Signals Received Power (RSRP) measured by the UE; controllingtransmission of a random access response message based on duration ofthe random access response window size that is derived by multiplyingthe first base value of the random access response window size with amultiplier factor corresponding to the coverage enhancement level of theUE; and controlling transmission of a MAC contention resolution messagebased on duration indicated by a timer value of the MAC contentionresolution timer that is derived by multiplying the second base value ofthe MAC contention resolution timer with the multiplier factorcorresponding to the coverage enhancement level, wherein the multiplierfactors are values of an information element of a radio resourceconfiguration that is different from the random access response windowsize and from the MAC contention resolution timer, wherein the values ofthe information element are used for indicating a number of repetitionsfor third and fourth messages of a random access procedure, and whereinthe fourth message is the MAC contention resolution message.
 4. A UserEquipment (UE) configured to perform radio communication according toNarrow Band-Internet of Things (NB-IoT), the UE comprising: a memory;and at least one processor coupled to the memory and configured to:receive system information, the system information including a firstbase value of a random access response window size, a second base valueof a Medium Access Control (MAC) contention resolution timer, andmultiplier factors corresponding to respective coverage enhancementlevels; determine a coverage enhancement level of the UE according toReference Signals Received Power (RSRP) measured by the UE; deriveduration of the random access response window size by multiplying thefirst base value of the random access response window size with amultiplier factor corresponding to the determined coverage enhancementlevel; derive a timer value of the MAC contention resolution timer bymultiplying the second base value of the MAC contention resolution timerwith the multiplier factor corresponding to the determined coverageenhancement level; receive a random access response message during thederived duration of the random access response window size; and receivea MAC contention resolution message during duration indicated by thederived timer value of the MAC contention resolution timer, wherein themultiplier factors are values of an information element of a radioresource configuration that is different from the random access responsewindow size and from the MAC contention resolution timer, wherein thevalues of the information element are used for indicating a number ofrepetitions for third and fourth messages of a random access procedure,and wherein the fourth message is the MAC contention resolution message.5. A method in a User Equipment (UE) performing radio communicationaccording to Narrow Band-Internet of Things (NB-IoT), the methodcomprising: receiving system information, the system informationincluding a first base value of a random access response window size, asecond base value of a Medium Access Control (MAC) contention resolutiontimer, and multiplier factors corresponding to respective coverageenhancement levels; determining a coverage enhancement level of the UEaccording to Reference Signals Received Power (RSRP) measured by the UE;deriving duration of the random access response window size bymultiplying the first base value of the random access response windowsize with a multiplier factor corresponding to the determined coverageenhancement level deriving a timer value of the MAC contentionresolution timer by multiplying the second base value of the MACcontention resolution timer with the multiplier factor corresponding tothe determined coverage enhancement level; receiving a random accessresponse message during the derived duration of the random accessresponse window size; and receiving a MAC contention resolution messageduring duration indicated by the derived timer value of the MACcontention resolution timer, wherein the multiplier factors are valuesof an information element of a radio resource configuration that isdifferent from the random access response window size and from the MACcontention resolution timer, wherein the values of the informationelement are used for indicating a number of repetitions for third andfourth messages of a random access procedure, and wherein the fourthmessage is the MAC contention resolution message.
 6. A non-transitorycomputer readable medium storing a program for causing a computer toperform a method in a User Equipment (UE) performing radio communicationaccording to Narrow Band-Internet of Things (NB-IoT), wherein the methodcomprises: receiving system information, the system informationincluding a first base value of a random access response window size, asecond base value of a Medium Access Control (MAC) contention resolutiontimer, and multiplier factors corresponding to respective coverageenhancement levels; determining a coverage enhancement level of the UEaccording to Reference Signals Received Power (RSRP) measured by the UE;deriving duration of the random access response window size bymultiplying the first base value of the random access response windowsize with a multiplier factor corresponding to the determined coverageenhancement level; deriving a timer value of the MAC contentionresolution timer by multiplying the second base value of the MACcontention resolution timer with the multiplier factor corresponding tothe determined coverage enhancement level; receiving a random accessresponse message during the derived duration of the random accessresponse window size; and receiving a MAC contention resolution messageduring duration indicated by the derived timer value of the MACcontention resolution timer, wherein the multiplier factors are valuesof an information element of a radio resource configuration that isdifferent from the random access response window size and from the MACcontention resolution timer, wherein the values of the informationelement are used for indicating a number of repetitions for third andfourth messages of a random access procedure, and wherein the fourthmessage is the MAC contention resolution message.